I am slowly remodeling the laundry room in the new house. Well, it's less of a remodel and more of "If you don't let me gut out this room and make it my own, I will go insane, and I will take you with me!" (Bonus points if you can name that mis-quote.) Anyway, I've demolished the old, nasty, unloved 37 year old vanity and have embarked upon my first plumbing adventure: replacing all the old plumbing and putting in a utility/laundry tub.

Before. All that yellow
is well-aged silicone.

At some point in the past someone had addressed an under-sink leak with a thick coating of silicone caulk on every joint and connection between the sink and wall.
I cut throught the black pipe and the second joint wasn't sealed on top so I was able to unscrew it, but I have to get the white pipe off the black pipe that exits the wall or I'll end up going into the wall with a plumber, so the silicone has to come off. And it's hard as a rock.

All the how-to's say the only way to remove cured silicone is elbow grease. There's chemicals which claim to do the job but they either don't work or require hazmat training. I finally found a note on some boat forum (which I can't find again, of course) that once you've scraped the majority of the silicone away, white vinegar can soften silicone residue enough to scrub it off. I soaked paper towels in white vinegar, wrapped them around the silicone, secured it with plastic wrap and went away for a couple hours. When I returned the rock-hard silicone had softened enough to work a screwdriver blade under the edge and stretch it away and off the joint.

The plastic wrap securing the vinegar-soaked paper towels. There's a bucket underneath, just in case.

The silicone, no longer the bane of my existence.

This took about 2 hours, most of which was wait time, and no special tools. While vinegar is one of those miracle chemicals, I'd recommend testing your surfaces before you soak with it. I'd also mention that bathroom fixtures are often sealed with silcone, so if you clean with straight vinegar regularly you will probably have to re-caulk from time to time (which isn't a bad idea anyway).